For many years, a great deal of attention has been devoted to techniques aimed at the effective separation of the titanium and iron constituents of titaniferous ores such as ilmenite. Nonselective chlorination techniques, i.e., in which the two metals are chlorinated simultaneously and the chlorides then separated from one another, have proven to be sufficiently effective that they are now practiced in the manufacture of titanium dioxide (TiO.sub.2) pigments, particularly by the so-called "chloride" process involving the oxidation of titanium tetrachloride (TiCl.sub.4). Such techniques are much less efficient than would be desired, however, since depending upon the iron content of the ore a considerable amount of costly chlorinating agent may be consumed in producing relatively useless iron chlorides as by-products. Conversion of the latter to metallic iron or some form of iron oxide would be deisrable to recover the chlorine content and to eliminate the waste disposal problem which has been associated with iron chlorides, but such conversion is difficult to achieve in economic fashion.
Other techniques for separating the iron and titanium constituents of ores have been devised that involve selectively chlorinating the iron content, thereby leaving an upgraded or beneficiated TiO.sub.2 fraction. While these have also achieved some measure of commercial importance, they have not served to lessen the problems associated with the formation of iron chloride by-products. Then, too, if one considers that TiCl.sub.4 is the desired intermediate, i.e., for producing a TiO.sub.2 pigment or metallic titanium, such beneficiation merely introduces an added step because the beneficiated fraction must still be chlorinated.
One approach that might appear to overcome the shortcomings of the above-noted techniques is that described in Wilcox U.S. Pat. No. 2,589,466. According thereto an ore such as ilmenite is said to be treated by chlorine in such a way that TiCl.sub.4 is produced without chlorination of iron. In repeated endeavors to follow the procedure of that patent as closely as possible, it has been found that a selective chlorination of the titanium does not occur; that is, that instead of selective chlorination the chlorine attacks iron either preferentially over titanium, or at least nearly equally, at temperatures up to essentially 1400.degree.C. That the process of the Wilcox patent would not result in a successful selective chlorination of the titanium constituent in ilmenite had been predicted on the basis of calculated equilibrium constants by S. Wilska, Suomen Kemistilehti, 29A, pages 220 to 225, 1956; Chemical Abstracts (1957), 4801(f). In C. C. Patel et al., Transactions of the Metallurgical Society of AIME, 218, pages 219-225 (April, 1960) it is further stated in reference to the Wilcox patent that "no justification can be found for the preferential chlorination at 1250.degree. to 1500.degree.C. of titania of roasted ilmenite. . ."
In the specification set forth hereinafter I describe my findings of a unique process for chlorinating the more useful titanium constituent of a titaniferous ore in a way that leaves the less useful iron constituent unchlorinated and, preferably, in the metallic state. That the titanium could be chlorinated without chlorinating the iron is contrary to what would have been expected from various technical articles, including those aforementioned as well as, more recently, S. H. Iqbal et al., Chemical Engineering World, Vol. VI, No. 8, pages 81-83 (1971). That such titanium chlorination could, moreover, be accomplished economically and efficiently using readily available starting materials is all the more unexpected.